1. Field of the Invention
The present invention relates to method for manufacturing capacitor of semiconductor device, and in particular to an improved method for manufacturing capacitor wherein a bonding layer is exposed via etch-back process without using a mask for opening the bonding layer to prevent degradation of adhesive property due to decrease in the area of the exposed bonding layer and oxidation of barrier metal layer.
2. Description of the Background Art
Generally, capacitor in DRAM memory cell functions as storage for electric charge to store information. Therefore, the capacitor requires sufficient capacitance and high reliability in long term repeated use, and the dielectric film must have insulation property of low leakage current.
As the integration density of devices gets higher, area allocated for unit cell is reduced, resulting in difficulties in obtaining sufficient capacitance for capacitor. Therefore, in order to increase capacitance of capacitor, the height of capacitor must be increased and the process margin between adjacent cells be reduced.
In order to increase the capacitance of a capacitor, a method wherein a noble metal is used as a lower electrode and a film having a high dielectric constant is used as a dielectric film.
Although not shown, a conventional method for manufacturing capacitor of semiconductor device is as follows.
An interlayer insulating film having a storage electrode contact hole therein is formed on a semiconductor substrate. Next, a tungsten contact plug filling a predetermined depth of the storage electrode contact hole is formed therein. A TiN layer serving as a barrier metal layer is formed on the entire surface to fill the remaining portion of the storage electrode contact hole.
Thereafter, the TiN layer is planarized via chemical mechanical polishing (“CMP”) to expose the interlayer insulating film so that the TiN layer remains only in the storage electrode contact hole. An alumina layer serving as a bonding layer is then formed on the entire surface. Next, the alumina layer is selectively etched via photolithography process to expose the TiN layer.
Next, a storage electrode consisting of a noble metal is formed on the bonding layer to contact the TiN layer.
In accordance with the conventional method for manufacturing capacitor of semiconductor device, a bonding layer is used to improve adhesive property of lower electrode consisting of a noble metal. However, a misalignment of opening occurs during the etching process of the bonding layer, which causes decrease of the thickness of the bonding layer and degradation of adhesive property. Moreover, oxygen atoms penetrate through the thin portion of the bonding layer to oxidize the barrier metal layer as shown in FIGS. 1 and 2, where FIGS. 1 and 2 are SEM photographs respectively showing oxidation of a TiN layer without and with a bonding layer in accordance with the conventional method for manufacturing capacitor of semiconductor device.
The oxidation of the barrier metal layer increase the contact resistance and the volume of the barrier metal layer, resulting in buckling at the interface of multiple layers constituting the lower electrode. When an oxide layer consisting of SiO2 exists on the alumina layer, the oxidation of metal barrier layer also occurs.